1. Field of the Invention
The present invention relates to an acoustic signal reproduction device having an acoustic characteristic compensation function.
2. Description of the Related Art
Conventionally, there have been known technologies for setting a transfer function from a reference sound source to a listener as a coefficient of a convolutional calculation to carry out the convolutional calculation regarding an audio signal using such a coefficient, so as to cause the listener to recognize, or perceive, the reference sound source. One example of such technologies is disclosed in Japanese Laid-open Publication No. 11-27800 (Title of the Invention: STEREOPHONIC SOUND PROCESSING SYSTEM).
However, the conventional system has difficulties in causing the listener to correctly recognize the position of the reference sound source. The reason for this is that the conventional system does not take into account an acoustic characteristic of reproduction speakers (or headphones) used by the listener. Also, the transfer function from the reference sound source to the listener cannot be correctly reproduced.
According to one aspect of the present invention, there is provided an acoustic signal reproduction device according to the present invention including a reproduction speaker and a signal processing section for generating an acoustic signal for causing a listener to recognize a sound as coming from a reference speaker. The signal processing section includes a compensation data input section for receiving compensation data from the outside of the acoustic signal reproduction device and a calculation section for calculating the acoustic signal based on the audio signal and the compensation data and outputting the acoustic signal to the reproduction speaker. The compensation data has a value H/C, where H is a transfer function from the reference speaker to a control point located in the vicinity of an ear of the listener, and C is a transfer function from the reproduction speaker to the control point located in the vicinity of the ear of the listener.
In one embodiment of the invention, the reproduction speaker is located nearest to an ear hole of the listener so as to be out of contact with the ear of the listener and the control point is located between the ear hole of the listener and the reproduction speaker.
In one embodiment of the invention, the compensation data is prestored in a recording medium and the compensation data input section receives the compensation data read from the recording medium.
In one embodiment of the invention, the compensation data input section receives the compensation data via a network.
According to another aspect of the present invention, an acoustic signal reproduction device including: first and third reproduction speakers for a right ear of a listener; second and fourth reproduction speakers for a left ear of the listener; a signal processing section for processing first through fifth audio signals to generate first and second acoustic signals for causing the listener to recognize first through third reference speakers, and third and fourth acoustic signals for causing the listener to recognize fourth and fifth reference speakers. The signal processing section includes: a compensation data input section for receiving first to tenth compensation data from the outside of the acoustic signal reproduction device; a first calculation section for calculating the first acoustic signal based on the first through third audio signals and the first through third compensation data and outputting the first acoustic signal to the first reproduction speaker; a second calculation section for calculating the second acoustic signal based on the first through third audio signals and the fourth through sixth compensation data and outputting the second acoustic signal to the second reproduction speaker; a third calculation section for calculating the third acoustic signal based on the fourth and fifth audio signals and the seventh and eighth compensation data and outputting the third acoustic signal to the third reproduction speaker; and a fourth calculation section for calculating the fourth acoustic signal based on the fourth and fifth audio signals and the ninth and tenth compensation data and outputting the fourth acoustic signal to the fourth reproduction speaker. The first compensation data has a value H1R/C1, the second compensation data has a value H2R/C1, the third compensation data has a value H3R/C1, the fourth compensation data has a value H1L/C2, the fifth compensation data has a value H2L/C2, the sixth compensation data has a value H3L/C2, the seventh compensation data has a value H4R/C3, the eighth compensation data has a value H5R/C3, the ninth compensation data has a value H4L/C4, and the tenth compensation data has a value H5L/C4. H1R is a transfer function from the first reference speaker to a control point located in the vicinity of a right ear of the listener, H2R is a transfer function from the second reference speaker to the control point located in the vicinity of the right ear of the listener, H3R is a transfer function from the third reference speaker to the control point located in the vicinity of the right ear of the listener, H4R is a transfer function from the fourth reference speaker to the control point located in the vicinity of the right ear of the listener, and H5R is a transfer function from the fifth reference speaker to the control point located in the vicinity of the right ear of the listener. H1L is a transfer function from the first reference speaker to a control point located in the vicinity of a left ear of the listener, H2L is a transfer function from the second reference speaker to the control point located in the vicinity of the left ear of the listener, H3L is a transfer function from the third reference speaker to the control point located in the vicinity of the left ear of the listener, H4L is a transfer function from the fourth reference speaker to the control point located in the vicinity of the left ear of the listener, and H5L is a transfer function from the fifth reference speaker to the control point located in the vicinity of the left ear of the listener. C1 is a transfer function from the first reproduction speaker to the control point located in the vicinity of the right ear of the listener, C2 is a transfer function from the second reproduction speaker to the control point located in the vicinity of the left ear of the listener, C3 is a transfer function from the third reproduction speaker to the control point located in the vicinity of the right ear of the listener, and C4 is a transfer function from the fourth reproduction speaker to the control point located in the vicinity of the left ear of the listener.
In one embodiment of the invention, the first reference speaker is a virtual sound source located on a straight line making an angle of about zero degrees with a straight line running through the center of the head of the listener, the second reference speaker is a virtual sound source located on a straight line making an angle of about +30 degrees with the straight line running through the center of the head of the listener, the third reference speaker is a virtual sound source located on a straight line making an angle of about xe2x88x9230 degrees with the straight line running through the center of the head of the listener, the fourth reference speaker is a virtual sound source located on a straight line making an angle of about +110 degrees to about +120 degrees with the straight line running through the center of the head of the listener, and the fifth reference speaker is a virtual sound source located on a straight line making an angle of about xe2x88x92110 degrees to about xe2x88x92120 degrees with the straight line running through the center of the head of the listener.
In one embodiment of the invention, the first through fourth reproduction speakers are included in headphones, the first reproduction speaker and the second reproduction speaker are located forward with respect to a vertical plane including a straight line connecting a hole of the right ear and a hole of the left ear of the listener, the third reproduction speaker and the fourth reproduction speaker are located rearward with respect to the vertical plane, and the first through fourth reproduction speakers are out of contact with the right ear and the left ear of the listener.
Thus, the invention described herein makes possible the advantages of providing: (1) an acoustic signal reproduction device which is capable of causing a listener to correctly recognize a sound as coming from a reference speaker by taking into account an acoustic characteristic of reproduction speakers (or headphones) used by the listener; (2) an acoustic signal reproduction device which is capable of compensating for an acoustic characteristic so as to be adapted for a reproduction speaker actually used by a listener; and (3) an acoustic signal reproduction device which is capable of lessening an influence of a difference in the head shape among individual listeners on acoustic characteristic compensation effects.
These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.